1. Field of the Invention
The present invention relates generally to air pollution control systems and, more specifically, to a biological purification system for polluted air.
2. Description of the Prior Art
The problem of air pollution in modern society has received increased attention in recent years. Air pollution from automobiles, industrial plants, released refrigerants, and the like have created serious environmental problems in the United States and other industrialized countries.
Increasingly stringent air pollution control regulations require the control of volatile organic compounds (VOC's) and toxic agents. However, most air pollution control systems presently available are very expensive to install and operate. In the case of smaller emission sources that emit pollutants at only low concentrations, it is often cost prohibitive to control these types of emissions using conventional technology. A need exists, therefore, for a simple, cost effective apparatus and method for removing pollutants from a source of polluted air in order to control air pollution from industrial operations, furnaces, paint booths, incinerators, and the like.
Biological disposal and purification systems have been known in the past especially in the case of fluid streams, such as waste water treatment. Typical prior art processes, such as that described in U.S. Pat. No. 5,064,763, issued Nov. 12, 1991, to Bentz feed polluted gases through one or more beds of biologically active material such as compost, wood chips, peat, soil, plant residues, or the like. The biologically active material containing the microorganisms is kept moist, as by passing the waste air through a humidifier before entry into the material, usually at the bottom of a filter bed. Pollutants in the gas stream are removed as they pass through the filter bed by diffusion into a wet film covering the filter particles. Biodegradation of the air pollutants takes place in this film. With a sufficient rate of biological activity, the pollutants are removed by aerobic degradation and form harmless byproducts, in the case of non-chlorinated VOC's, water and carbon dioxide. While the biologically active material is kept "moist", the waste gases do not contact a liquid stream, as might be utilized in a traditional "wet scrubbing" operation.
U.S. Pat. No. 4,959,084, issued Sep. 25, 1990, to Wolverton et al., shows a combined air and water pollution control system. The pollution control system includes an exhaust for directing polluted gases out of a furnace and a fluid circulating system which circulates fluid, such as waste water, from a source past the furnace where the fluid flow entrains the pollutants from the furnace. The combined fluid and pollutants are then directed through a rock/plant/microbial filtering system. A suction pump is used to move the treated waste water from the filter system past the exhaust to again entrain more pollutants from the furnace. The system utilizes a venturi which would require a high velocity air stream and consequently excessive horse power requirements. The venturi could, in some instances, also constitute a restriction in the gas flow which would cause undesirable pressure or velocity changes within the system.
It is an object of the present invention to provide a biological air pollution control system which is simple in design and economical to manufacture and which converts air pollutants into harmless and/or odorless forms, thereby preventing such pollutants from entering the atmosphere.